The tensile properties of TiO2-filled poly(vinyl acetate) were studied at strain rates of 100%/min. to 5,000%/min. at 25°C. after exposure to relative humidities of 10, 25, 51, 70, and 90% for 160 hr. Filler concentrations studied were 0, 10, 20, 30, and 40 wt.-% TiO2. The change in tensile properties with greater humidity was dependent on filler content. As the filler content increased, strength was lowered, elongation increased, and stiffness decreased with greater humidity. Generally, changes in tensile properties with humidity were less pronounced at higher strain rates. A mechanism is proposed where H2O alters the packing of polymer chains and affects the interaction of filler with polymer.